The present invention relates to a shield connector which is used for electrically interconnecting electronic appliances mounted on an automobile or the like, for example.
A plurality of electronic appliances are mounted on the automobile as a movable body. Therefore, for the purpose of transmitting electric power and signals to these electronic appliances, wire harnesses are arranged in the automobile. The wire harnesses are provided with a plurality of electric wires and connectors.
The electric wire is a so-called shielded wire including a core wire having electric conductivity and a shielding part formed of insulating synthetic resin for shielding this core wire. As the connector, shield connectors of various types such as a shield connector 700 (exemplified in FIGS. 5 to 7), for example, have been heretofore used.
The shield connector 700 as shown in FIGS. 5 to 7 is superposed on a printed wiring board and fixed to the relevant printed wiring board. The shield connector 700 includes an inner housing 701 formed of insulating synthetic resin, a plurality of terminal metals 702 which are fitted to the inner housing 701, and an inner shield shell 703 formed of conductive metal, an outer housing 704 formed of insulating synthetic resin, and an outer shield shell 705 formed of conductive metal.
The inner housing 701 is formed in a substantially quadrangular pillar shape. The terminal metal 702 is formed of conductive metal in a rod-like shape. One end portion 702a of the terminal metal 702 is arranged so as to pass through the inner housing 701, and the other end portion 702b is bent at a substantially right angle from the one end portion 702a to be arranged outside of the inner housing 701.
The inner shield shell 703 is obtained by folding a sheet metal. The inner shield shell 703 is integrally provided with a shell body 706 which contains therein the inner housing 701 in such a manner that its inner face is tightly superposed on an outer face of the inner housing 701, and a fixing piece 707 which is erected from the shell body 706 and adapted to be fixed to a pattern of conductors on the printed wiring board and so on.
The outer housing 704 is formed in a quadrangular tubular shape for containing the inner shield shell 703. The outer housing 704 is provided with a wall part 704a at a position close to its one end at an opposite side to an end with which a mating connector is engaged. The wall part 704a is provided with an opening along an outer periphery of the inner shield shell 703, so that the inner shield shell 703 is press-fitted into this opening thereby to be fixed inside the outer housing 704.
The outer shield shell 705 is obtained by folding a sheet metal. The outer shield shell 705 is integrally provided with a shell body 708 which contains therein the outer housing 704 in such a manner that its inner face is tightly superposed on an outer face of the outer housing 704, a pair of elastic contact pieces 709 which are internally erected from the shell body 708 and brought into elastic contact with the inner shield shell 703, and a plurality of fixing pieces 710 which are erected from the shell body 708 and adapted to be fixed to the pattern of the conductors on the printed wiring board and so on.
The shield connector 700 as described above is engaged with the mating connector, and at the same time, introduces electrical noise which is going to leak to the exterior from the terminal metals 702 and electrical noise which is going to enter into the terminal metals 702 from the exterior, to an earth circuit, from the inner shield shell 703 and the outer shield shell 705, respectively through the fixing piece 707 of the inner shield shell, the fixing pieces 710 of the outer shield shell 705, and the pattern of the conductors on the printed wiring board.
It is to be noted that there is no information concerning a document of the prior art to be disclosed, because there has been no prior art that the applicant knows at a time of filing this patent application.
The inner shield shell 703 and the outer shield shell 705 are electrically connected to each other by a pair of the elastic contact pieces 709 which are provided at inside of the outer shield shell 705. Then, due to this connection, electric current which flows through respective surfaces of the shield shells 703, 705 together with occurrence of noises flows from one of the shield shells to the other shield shell by way of the elastic contact pieces 709.
The noise emitted from the electric power and signals of the electronic appliances includes a lot of high frequency signal components, and the high frequency signal has such property that it is unlikely to flow, in case where a surface area is small. In the above described shield connector 700, because the inner shield shell 703 and the outer shield shell 705 are electrically connected by means of the elastic contact pieces 709, a contact area between them is very small (In short, the surface area is small). For this reason, the electric current together with the noise cannot efficiently flow between the shield shells 703 and 705, and a potential difference occurs on the respective surfaces of the shield shells 703, 705, which results in deflected distribution of the electric current. Accordingly, there has been such a problem that the noise (electromagnetic wave) caused by this deflected distribution of the electric current is emitted to the exterior of the shield shells 703, 705.